Generation of high pressure steam with low salt content



P 1941- o. HARTMANN 2,238,562

GENERATION OF HIGH PRESSURE STEAM WITH LOW SALT CONTENT FiledMarch 6, 1939 Ira/enforobo/larfrnanh,

Patented Apr. 15, 1941' 'GENERATION OF HIGH PRESSURE STEAM WITH LOW SALT CONTENT Otto Hartmann, Kassel-Wilhelmshohe,

Germany Application March 6, 1939, Serial No. 260,216 In Germany March 23, 1938 Claims. (01. 1222-33) This invention is directed to the generation'of high pressure steam with a low salt content from a feed water containing so much salt as to make the water practically unusable.

It is an object of the invention to generate steam substantially free of salt from a feed water which contains a substantial quantity of salt, the steam being washed in the boiler in which it is generated.

A further object of the invention isv to generate steam substantially freeirom salt from feed water containing salt bypassing the steam bubbles formed in the feed water through a layer of purer water which substantially filters the salt from the generated steam.

A further object of the invention is to generate steam substantially free of salt by covering the feed water having a large salt content, and having a relatively high specific gravity, with a layer of .water substantially free of salt and having a relatively low specific gravity, the steam evaporated in the feed waterof high specific gravity being efiectively washed and freed from salt in the layer of water of low specific gravity.

In the generation of high pressure steam, one

of the principal problems is to obtain a steam which is substantially free of salt. It; is, of course, understood that the salt carried along in dissolved or gaseous state by the steam evaporated in the boiler, deposits or precipitates on the nozzles and blades of a turbine, and that such deposits not only destroy the efficiency of the turbine, but also cause a destruction of the turbine through corrosive action. Various methods are employed to reduce the salt content of the generated steam, one common method being the condensing of the used steam and returning the water to the boiler, withonly additional salt free feedwater amounting to 3% to 5% being'required. Washing drums have also been provided with high pressure boilers, the freshly generated steam being passed through these washing drums. Also the washing of the steam has been attempted by passing the freshly generated steam over surfaces wetted by fresh water in the boiler drum. These methods are not satisfactory because of the additional water required in the washing drums, and because of the heavy and expensive equipment necessary for condensers and washing drums as well as the large washing surfaces necessary. Obviously the additional equipment is expensive as well as being bulky and cumbersome. Furthermore, even with the use of these auxiliaries, it is almost necessary to use chemically pure feed Water, the production of which is, in itself, an expensive operation. Likewise, steam converters and other auxiliaries all have their disadvantages. I j The problem is solved,faccording to the instant invention, by-a very simple and efiective means by'which the principal feedv water need not be chemically pure water. The method is especially advantageous in boiler systems where the steam is indirectly generated. In general, thejfeed water in the boiler is not circulated, and is only agitated by the steambubbles being evaporated therein. The feed water, having a relatively high salt content, is contained in the lowest part oi the boiler, and over top of this feed water, a layer of water substantially free of salt is placed. The water in this upper layer may be obtained from a condenser., The upper layer of water, being substantially pure, has a lower specific gravity than the feed water in the lower part of thereceptacle, and consequently the two layers do not tend tomix. water in the upper layer is constantly replenished so that the upper layer is efiectively maintained despite boiling. The steam bubbles evaporated in the lowerv layer of water pass through the upper layerv of pure water, and in so passing, the'steam is washed, giving up its salt. A boiler can have, according to' this invention, of the total water composed of water with a high salt content and forming the lower water layer, and 20% as pure water forming the upper layer. From such steam can be produced which has such a low salt content that no appreciable precipitation of salt takes place in the turbine. Although the method is usable in the direct generation of steam, it is especially advantageous in boilers using indirect generation of steam, inasmuch as the tubes of the primary steam gener-.

ating system can be evenly distributed throughout the boiler ot the secondary generating system, and thus a very uniform evaporation of the able for the Loeffier type boiler, United States Patent No. 1,740,524, the non-circulating water content of which is heated by blown-in superheater steam.

A means by which the objects of this inven- Under operating conditionsithe Indirect steam boilers tion are obtained is shown in the accompanying drawing; in which:

Fig. 1 is a boiler arranged according to the instant invention; and,

Fig. 2 is a cross sectional view on the line 22 of Fig. 1.

Fig. 1 illustrates the method applied to the secondary boiler of an indirect steam generating system.

Within the boiler 2 are placed tubes 4 which are connected by headers 6 and tubes 8 to the primary steam generating system. Feed water.

having a high salt content, is fed to the lower portion of the boiler from pump through pipe l2 to valve [4, and from valve I4 is admitted into and evenly distributed in the lower portion of the boiler by being passed through a per.- forated tube l6 extending the length of the boiler.

This feed water consists of a stronglye conthat this layer or strata of feed water, which is denoted as a in the drawing, comprises substantially 80% of the water in boiler drum 2.

Substantially pure salt free, feed water, which may be condensed steam, is forced from feed pump through pipe line 22 into the upper portion of the boiler. Pipe line 22 connects with valve 24, from which the substantially pure feed water is passed'into' a flume 26, the water overflowing the sides of the fiume to form a layer b of substantially pure feed water on top of the layer a. The layers a and I) do not tend to mix because of the difference in specific gravity therebetween. The water in layer b should have about the same temperature as the generated; saturated steam, so that the water in layer b will not sink down and mix with the water in layers. However, the water in layer b can be colder, it the salt content of the water in layer a is increased. In the cold upper strata b, the salt rising in the steam bubbles from. the layer a. is not only dissolved and separated ofi, but the Sublimated salts in gaseous state contained in the steam bubbles are solidified in the out the boiler, without danger of mixing the two layers. The steam generated is taken off through dry pipe 21 to a point of use through conduit 28.

The method described has the further advantage in that existing types of indirect steam generating boilers can be used with but slight changes. For example, boilers of the Schmidt or Lofiler types need only be provided with the perforated tube I6 and the fiume 26, the tube and fiume being connected to separate supply systems of feed water. The cost of equipment is thus materially reduced, and the cost of washing the steam is further reduced because only a small partof the water fed to the boiler needs to be substantially pure salt free water.

Having now described my invention, what I claim and desire to secure by Letters Patent of the United States is:

1. A method of generating high pressure steam substantially free from salt in a boiler without circulating water, comprising feeding water having ahigh salt content into the lower portion of the boiler, feeding water having a low salt content into the upper portion. of the boiler as a layer covering said first fed water, and heating said boiler to form steam bubbles rising from said first fed water, said bubbles passing through and being washed in said second fed water.

2. A method as in claim 1, said second fed water being supplied to said boiler at a temperature lower than that of said first fed water.

3, A method as in claim 1, said heating comprising the heating in the secondary system of an indirect steam generating boiler.

4. A method of generating high pressure steam substantially free from salt in a boiler without circulating water comprising continuously feeding water having a high salt content into the lower portion of the boiler, continuously feeding water having a low salt content into the upper portion of the boiler as a layer covering said first feed water, heating said boiler to form steam bubbles rising from said first fed water, and removing the steam from said boiler after it has been Washed by passing through said second fed water.

5'. An apparatus for the generation of substantially salt free high pressure steam comprising a boiler, heating means in said boiler, first means for uniformly distributing a feed water of high specific gravity over the lower portion of said boiler, second means for distributing uniformly a feed water of low specific gravity over the feed water of high specific gravity, a first source of feed water having a high specific gravity, said first means being connected to said first source; a second source of feed waterlhaving a low specific gravity, and said second means being connected to said second source.

OTTO HARTMANN. 

